Help me with welding woes

I was wondering what size mig i would need to weld .120dom i know it is barly under 1/8" thick but i have been told that you need a big 250 amp mig to get good penatration but i would think a smaller mig around 150 to 170 amp rated up to 1/4" would work good so i need some help from the welders and brighter people than myself.

Or you can get the Lincoln Weld-Pak 100 for $328 from Home Depot. I own it and weld 1/8" with no problem at all. It can weld 1/4" with a couple passes, but 1/8" single pass is no problem. You can get the Mig kit for an additional $78 from Home Depot as well. It's rated at 100amps and works just fine. Although I have a 225amp Lincoln ARC for the big jobs....

I agree with waxer, the little 110 volt migs are just fine for 1/8" stuff. I would get the bottle and regulator though, its a lot easier to get the appropriate weld size with gas sheilded wire than flux core. Weld strength should be fine with either as the welding wire is usually rated at 70,000 psi tensile. I've welded a fair bit of 1/8" material with my little 80 amp machine and it does just fine, although it is at its limit doing it (I bought it for body work...)
One thing that will help in the strength department is good joint preparation, bevel the edges to be welded. A little pre-heat helps too.

Personally I think there is nothing quite as satisfying as building your own parts (when possible). Its not rocket science but it helps to have all the right tools. Too many salesmen want to sell you a $4000 professional welding machine that requires professional re-wiring of your garage.....

Just shop around a little and find the most machine you can afford for the welding you need it to do. I didn't need a big machine for home (got a few a work ) so my little 110 job was just the ticket.

The only issue I have with the less expensive machines (like mine) is that the wire in the gun is always 'live'. I am used to the 400 amp machines at work so I never thought to ask. On my home machine if you touch the wire to the work even without pulling the trigger it'll flash and spark, the machine at work doesn't do that. The wire is energized when you pull the trigger on the gun, and thats the way it should be. I can't count how many times I've seen spots for a few minutes because of that. Try and find a machine where the wire is energized by pulling the trigger, not 'always on'. You'll thank yourself later.

I know my MIG is good enough to handle 1/4" thick stuff. I paid $500 for mine at Sears. Its rated at 150amp. Like Rene said, good metal preperation (like beveled edges) and some preheating (not on the thin stuff, but on the thick stuff) will definately do the trick. Mine is also the pull the trigger when wanting to weld. Definately get the gas.
Btw, Rene, in my opinion, is the "Welding Master" Taught me everything I know about welding. This man definately knows his stuff when it comes to welding...and other things ofcourse Thanks Rene!
Boss

Yeah, its either Miller or Lincoln, I'm not 100% sure to be honest with you, but I know its one of them. All Craftsman did was put their Name/seal on it. I think its a great welder. The only problem I have with it is that when I'm welding thicker metals, like I have the voltage on 6 to 8, my power in my garage keeps cutting out on me. Then I have to go to the circuit breaker and turn the power back on. I know, that's not the MIGs fault, so therefore, I have no problems with it! take care.
Boss

I don't think that Sears manufactures anything. All of the stuff with their brand names on them are made by other companies. Their Crafstman wrenches are made by Western Forge, here in Colorado Springs. Whirlpool makes a lot of the Kenmore applicances, etc.

Ok, I've got a question for Rusty or anyone out there that knows. In my current project, I will be cutting and splicing the frame of a K30. Basically making a Blazer with a 1 ton frame and gear. Now, I know how to weld but I have never tried to use one of these small 110 MIG units. I was wondering if a small MIG will be able to make suitable, strong welds on that frame without multiple passes. I no longer have access to the larger unit that I used years ago and I have been considering one of these as an addition to my home shop.

I think it should be done with a welder that has a better duty cycle than the 110 volt machines have. Once you have it all prepped and pre-heated you don't want to start welding only to have to wait for the machine to cool down so you can continue.
I'm not sure about the vehicle safety laws where you are but here welding a frame is frowned upon and usually requires an independant third party inspection of the welding done....
I would make sure to bevel the edges of the joint to be welded to ensure 100% penetration of the joint and even then I would use some form of fish plating over the joint as added insurance that it is not the weakest part of the frame.
HTH

Thanks, how far can you make it on a frame with one of these light boxes before giving it a rest? I ran a frame machine for a few years but I had a full grown MIG that could go all day (well, long enough) on something like a frame. I don't want to run multiple passes due to higher potential for oxygen contamination problems and/or creating a brittle frame that will break beside the weld. Not to mention, having to let it cool between each cycle before starting again is a pain.

Also, I'm not a fan of large fish plates because they can create a rigid area that the adjoining frame will work against while flexing and tend to break right beside it. I’ve had to fix a couple of frames that broke right beside a foot long plate used in a previous repair. I usually just put a 2" wide plate behind the weld so I don’t have to worry about blowing through with 45 degree beveled edges on the but ends and pre-heat. This seems to have worked well for me on some heavy work trucks I did (logging trucks and such).

Other than some stuff I did long ago (my own stuff, before the shop), I've never had a frame that I welded break (at least that I know about). As far as safety laws, this is a dedicated trail rig so inspection is not a problem. I just don't want to ruin the frame. I guess I'll probably get one of the small Lincoln (like the MIG 15) units for my shop (it's not like I plan on doing this all the time) for normal fab stuff. I may try to rent/borrow something heavier for the frame if I can (not likely). If not, my neighbor has a big shop grade arc welder that I could use but I was never that good with an arc.

On second thought, this is not something I want to screw up trying to make do without the right tools. I think I'll just get it lined up and tacked in place before trailering it to a real shop with a real machine. I'm rusty anyway (no pun intended ) after all these years. It's been 7 years since I last did any welding after all...

Most of the little 110 volt machines have a duty cycle of about 20% running flat out, which it would be doing a frame. I don't think you could complete the weld in one pass in under 2 minutes. which means you'd be at best about halfway before the machine needs an 8 minute rest.
The backing bar sounds like the way to go. I've seen a bolted fish plate before as well that would at least allow some frame flex in the area.
Sounds like you have a good plan and quite a cool project, good luck.

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